Earth-boring tools are commonly used for forming (e.g., drilling and reaming) bore holes or wells (hereinafter “wellbores”) in earth formations. Earth-boring tools include, for example, rotary drill bits, core bits, eccentric bits, bicenter bits, reamers, underreamers, and mills.
Earth-boring rotary drill bits have two primary configurations. One configuration is the roller cone bit, which typically includes three cones mounted on supporting bit legs that extend from a bit body, which may be formed from, for example, three bit head sections that are welded together to form the bit body. Each bit leg may depend from one bit head section. Each roller cone is configured to spin or rotate on a bearing shaft that extends from a bit leg in a radially inward and downward direction from the bit leg. The cones are typically formed from steel, but they also may be formed from a particle-matrix composite material (e.g., a cement composite such as cemented tungsten carbide). Cutting teeth for cutting rock and other earth formations may be machined or otherwise formed in or on the outer surfaces of each cone. Alternatively, receptacles are formed in outer surfaces of each cone, and inserts formed of hard, wear resistant material are secured within the receptacles to form the cutting elements of the cones.
The roller cone drill bit may be placed in a bore hole such that the cones are adjacent the earth formation to be drilled. As the drill bit is rotated, the roller cones roll and slide across the surface of the formation, which causes the cutting teeth to crush and scrape away the underlying formation.
It is known in the art to apply wear-resistant materials, such as “hardfacing” materials, to the formation-engaging surfaces of rotary drill bits to minimize wear of those surfaces of the drill bits caused by abrasion. For example, abrasion occurs at the formation-engaging surfaces of an earth-boring tool when those surfaces are engaged with and sliding relative to the surfaces of a subterranean formation in the presence of the solid particulate material (e.g., formation cuttings and detritus) carried by conventional drilling fluid. For example, hardfacing may be applied to cutting teeth on the cones of roller cone bits, as well as to the gage surfaces of the cones. Hardfacing also may be applied to the exterior surfaces of the curved lower end or “shirttail” of each bit leg, and other exterior surfaces of the drill bit that are likely to engage a formation surface during drilling.
During drilling, drilling fluid is pumped down the wellbore through the drill string to the drill bit. The drilling fluid passes through an internal longitudinal bore within the drill bit and through other fluid conduits or passageways within the drill bit to nozzles that direct the drilling fluid out from the drill bit at relatively high velocity. The nozzles may be directed toward the cones and cutting elements thereon to clean debris and detritus from the cones and prevent “balling” of the drill bit. The nozzles also may be directed past the cones and toward the bottom of the wellbore to flush debris and detritus off from the bottom of the wellbore and up the annulus between the drill string and the casing (or exposed surfaces of the formation) within the wellbore, which may improve the mechanical efficiency of the drill bit and the rate of penetration (ROP) of the drill bit into the formation.
It is known in the art to use flow tubes to direct drilling fluid to a nozzle and out from the drill bit, particularly when it is desired to direct drilling fluid past the cones and toward the bottom of the wellbore. Such flow tubes may be separately formed from the bit body, and may be attached to the bit body (e.g., bit head section or bit leg) by, for example, welding the flow tubes to the bit body. A fluid course or passageway is formed through the bit body to provide fluid communication between the interior longitudinal bore of the drill bit and the fluid passageway within the flow tube.
As drilling fluid is caused to flow through the flow tube, the drilling fluid erodes away the interior surfaces of the flow tube. Such erosion may be relatively more severe at locations within the flow tube at which the direction of fluid flow changes, since the drilling fluid impinges on the interior surfaces of the flow tube at relatively higher angles at such locations. This erosion can eventually result in the formation of holes that extend completely through the walls of the flow tube, thereby allowing drilling fluid to exit the flow tube before passing through the nozzle, which eventually leads to failure of the designed hydraulic system of the drill bit. When the hydraulic system of the drill bit fails, the rate of penetration decreases and the drill bit becomes more susceptible to “balling.” Ultimately, the drill bit may fail and need to be replaced.
In view of the above, there is a need in the art for fluid passageways and flow tubes for earth-boring tools and components thereof that are relatively more resistant to erosion, for methods of forming such earth-boring tools and components, and for methods of increasing the erosion resistance of fluid passageways and flow tubes of earth-boring tools and components.